学习笔记-计算当前日期为星期几

// 判断是否为闰年
- (BOOL)judgeIsLeapyears:(NSInteger)year{
    if ((year %4 == 0 && year % 100 != 0) || year % 400 == 0) {
        return YES;
    }else{
        return NO;
    }
}

- (NSInteger)judgeDate:(NSString *)date{
// 此处使用的日期格式为xxxx-xx-xx
    NSArray *array = [date componentsSeparatedByString:@"-"];
    NSInteger year = [array[0] integerValue];
    NSInteger month = [array[1] integerValue];
    NSInteger day = [array[2] integerValue];
    BOOL isLeapyear = [self judgeIsLeapyears:year];
    NSInteger FebDays;// 二月天数
    NSInteger n = 0;
    if (isLeapyear) {
        FebDays = 29;
    }else{
        FebDays = 28;
    }
    switch (month) {
        case 1:n=day;break;
        case 2:n=31+day;break;
        case 3:n=31+FebDays+day;break;
        case 4:n=31+FebDays+31+day;break;
        case 5:n=31+FebDays+31+30+day;break;
        case 6:n=31+FebDays+31+30+31+day;break;
        case 7:n=31+FebDays+31+30+31+30+day;break;
        case 8:n=31+FebDays+31+30+31+30+31+day;break;
        case 9:n=31+FebDays+31+30+31+30+31+31+day;break;
        case 10:n=31+FebDays+31+30+31+30+31+31+30+day;break;
        case 11:n=31+FebDays+31+30+31+30+31+31+30+31+day;break;
        case 12:n=31+FebDays+31+30+31+30+31+31+30+31+30+day;break;
    }
    NSInteger num = (year-1)+(year-1)/4-(year-1)/100+(year-1)/400+n;
    return num % 7;// 1-6对应星期一到星期六，0为星期天
}